Auxiliary Heating for Steam Generator Startup
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Solution Overview
Problem
Steam generators, such as sub-critical and super-critical steam generators, face challenges in reducing start-up time and minimizing thermal stress on components, leading to increased costs and environmental impact due to prolonged transition from standstill to firing mode, primarily due to the need for extensive auxiliary fuel use and slow water filling processes.
Innovation Solution
The implementation of auxiliary heating devices and a system for degassing and pre-heating water, including spargers and electric heaters, to rapidly warm critical components and fill water circuits, ensuring components remain ductile and reducing thermal stress, while also recirculating degassed water to maintain efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the steam generator transitions from standstill to firing mode quickly, then the return to service time is reduced and productivity is improved, but thermal stress on components increases and reliability deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-heating critical components (boiler drum, waterwall tubes, furnace top-end piping) before the actual firing mode transition. Auxiliary heating devices are activated during the water filling process to maintain component temperatures above the brittle-ductile transition point, enabling faster startup while preventing thermal stress damage.
2Productivity
If auxiliary heating devices are installed to warm components rapidly, then the start-up time is reduced and productivity is improved, but device complexity increases
Solution Approach 1:
The auxiliary heating devices serve multiple functions: they pre-heat components during water filling, maintain component temperatures during standby periods, and prevent condensation in the water-steam separator. This multi-functionality justifies the added device complexity by delivering multiple benefits from a single system addition.
3Productivity
If water filling is performed rapidly, then the transition time is reduced and productivity is improved, but thermal stress on components increases
Solution Approach 1:
The patent changes the temperature parameter of the filling water by using pre-heated water from the water-steam separator or economizer outlet. This temperature adjustment allows rapid water filling without creating excessive thermal stress, as the water temperature is coordinated with the component temperature to maintain safe temperature differentials.
4Temperature
If auxiliary fuel is used extensively during startup, then component warm-up is achieved, but energy consumption and environmental impact increase
Solution Approach 1:
The system applies self-service by using the steam generated during normal operation to pre-heat the filling water and warm components during startup. The water-steam separator and economizer outlet water are utilized as heat sources, reducing or eliminating the need for auxiliary fuel combustion while still achieving necessary component warm-up temperatures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the 'return to service' time of steam generators, minimizes auxiliary fuel consumption, and decreases environmental impact by enabling faster, more efficient start-ups and reducing thermal stress on components, thus enhancing operational responsiveness and cost-effectiveness.
Implementation Method 1
a first auxiliary heating device is disposed on a water-steam separator for heating the water-steam separator. a second auxiliary heating device is disposed at least on a part of the furnace top-end piping for heating the furnace top-end piping
Implementation Method 2
a third auxiliary heating device is installed to provide the heat to keep a deaerator at the required condition, in particular when a feedwater startup pump is engaged
Implementation Method 3
a fourth auxiliary heating device is disposed on the economizer for heating the economizer
Implementation Method 4
an economizer outlet feedwater line includes the fifth auxiliary heating device which heats or (pre-)heats the water discharged by the economizer
Implementation Method 5
The implementation of auxiliary heating devices and a system for degassing and pre-heating water, including spargers and electric heaters
Implementation Method 6
The implementation of auxiliary heating devices and a system for degassing and pre-heating water, including spargers and electric heaters
Data Source
AI summary
A system for readying sub-critical and super-critical steam generator, a servicing method of the sub-critical and the super-critical steam generator and a method of operation of sub-critical and super-critical steam generator is provided. The steam generator includes a first auxiliary heating device disposed on at least one water-steam separator for heating the at least one water-steam separator, and/or a second auxiliary heating device disposed at least on a part of furnace top-end piping for heating the furnace top-end piping. The auxiliary heating devices are heating steam producing components of the steam generator and thus allowing to keep them above the temperature in which materials creating the steam producing components are brittle. The method includes recirculation of the water through the steam generator.